public class Solution3 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @return ListNode类
     */
    public ListNode ReverseList (ListNode head) {
        // write code here
        if (head == null || head.next == null) {
            return head;
        }

        ListNode sur = head.next;
        ListNode pser = head;
        head.next = null;
        while (sur != null) {
            pser = sur;
            sur = sur.next;
            pser.next = head;
            head = pser;
        }
        return head;
    }
}